Have fun!
I did that for awhile but it got to a point where I had to dye my hair every month and it was frying my hair.
It was brittle, felt like straw, the color would fade quickly, it broke easily and I had split ends everywhere.
The dyeing process pretty much punches holes in your hair.
The more you dye, the more damage accumulates and there is no repairing it - it just has to grow out.
So, I eventually switched to henna.
My natural color is brown with streaks of grey.
With the henna I get a beautiful auburn and the grey becomes coppery highlights.
I use body art quality henna about once every 8 weeks and my hair is strong, smooth, shines, I no longer have a single split hair on my head and I can grow it a long longer than I use to be able to.
I like knowing I can get a beautiful color with a ground up powdered plant and vinegar.
My scalp loves it, I get no exposure to PPD like I did with commercial dyes.
The process does take longer.
I mix my mix up the night before and keep it slightly warm for dye release and then I smush it on my hair, wrap it in cling wrap and a towel and let it sit for about 5 hours before washing it out with a cheap conditioner.
The color is a little bright for 24 hrs then mellows/oxidizes slightly and I'm a glorious red head once again!
I get that red is not everyone's cup of tea.
If you want to try more for brown, you can mix some indigo in with your henna.
In case you are interested, here's a site that tells you more than you would ever want to know about it (but I just LOVE their site!):
http://www.hennaforhair.com/mixes/